The invention relates to a method for disconnecting passenger conveying systems, in particular escalators and moving walkways.
So-called safety chains are frequently used in prior art, wherein limit switches, for example for the hand-rail intake, the step intake or the like are interconnected with respect to the signals. In the past, the elements for disconnecting the drive or drives of the individual passenger conveying systems, in particular for escalators or moving walkways, were actuated directly via this safety chain. An interruption in the safety chain therefore automatically caused the escalator or moving walkway to stop.
However, the disadvantage of this method is that other structural components, such as the error diagnosis device, cannot be optimally dimensioned because they are also tied into the safety circuit and consequently are influenced by the safety chain or its structural components with respect to function. The reason for another disadvantage is that only an individual evaluation of the added limit switches is possible. A parallel evaluation does not exist because each limit switch interrupts the voltage supply to the respectively other limit switches.
It is the object of the invention to provide a method for disconnecting passenger conveying systems as well as a safety circuit for these systems. The method allows the optimum dimensioning of the components for the error diagnosis, so that the component(s) is (are) independent of the otherwise parallel-positioned disconnecting elements at the end of the safety chain. The goal is furthermore to obtain an evaluation of several activated limit switches without resulting in mutual obstruction.
This object is achieved with a method for disconnecting passenger conveying systems, in particular escalators and moving walkways, in that the error behavior of functional units is monitored with switching elements and their signals are combined to form a safety chain. The signals from the functional units, along with the signals from the drive monitoring unit, are then supplied to at least one pilot control unit before the disconnect signal is supplied to the disconnect contact for the drive or drives, in dependence on the error behavior of the respective functional unit.
Advantageous modifications of the method according to the invention follow from the associated dependent claims.
With respect to the subject matter, this goal is also reached with a safety circuit for passenger conveying systems, in particular for escalators and moving walkways, which includes switching elements that are combined to form a safety chain in the area of functional units, at least one drive monitoring unit, at least one pilot control unit and at least one disconnect contact for the drive and the drives. For this, the signals for the safety chain and those for the drive monitoring unit can initially be supplied to the pilot control unit.
Advantageous modifications of this safety circuit follow from the associated dependent claims.
The safety chain principle according to the invention no longer leads directly to the disconnect elements for the drive or drives, but indirectly via at least one pilot control unit. This measure permits an optimum dimensioning of the structural components for the error diagnosis because they are now independent of the safety circuit.
In addition to the safety chain, the safety relays for the respective pilot control unit can also be actuated via processors in the drive-monitoring unit, wherein opto-couplers are preferably used for this.
The function of the safety relays, primarily the decay in the disconnect contacts, is respectively monitored via the aforementioned microprocessors, wherein opto-couplers are used in this case as well for reasons of circuit engineering.
The pilot control units, which preferably have a redundant layout, each comprise at least one resistor (series resistor) and at least one capacitor that is operatively connected to at least one relay coil.
According to another inventive idea, the drive monitoring unit has a redundant layout, so that two microprocessors, which preferably monitor each other, together with the signals from the safety chain, are fed to the respective pilot control units.
The signals for the safety chain and/or the drive monitoring in this case are conducted with an operating voltage of 24 V.
Each relay coil is laid out for a voltage of 12 V, even though the supply voltage for the circuit component actually is 24 V. These voltage values are necessary to ensure a secure disconnecting or switching on of the relay coil, despite the low disconnect voltage or the high pick-up voltage. The operating voltage of 24 V is distributed with the ratio of resistors (series resistors) to relay coils.
At the moment of switching it on, the relay coil requires a voltage of at least 9 V (or more with increased temperatures). The capacitor characteristic of being conducting during the switch-on moment is used for that reason. The resistors (series resistors) are thus bridged, meaning they become ineffective. During the switching on, the voltage divider ratio favors the relay coil, thereby ensuring that the pick-up voltage is reached securely.
The capacitor, which is charged up during the switching-on operation, thus no longer influences the voltage ratios during the shutdown operation (very high resistance). The influence is instead exerted by the resistance ratios for the complete safety circuit. The voltage-divider ratio is subsequently determined parallel to the limit switches by the series resistors and is adjusted such that the value falls securely below the disconnect voltage and the available output is no longer sufficient to actuate the relay coils.
The subject matter of the invention is shown in the drawing with the aid of an exemplary embodiment and is described as follows.